Sometimes the best way to approach withdrawing from a substance is do to it with medical help at a facility specializing in detox or at a mental health facility. Opiates do have unpleasant withdrawal symptoms and in a medical setting they will give medications to help control symptoms and wean you off until you are completely free and clear of them. Then, they usually have some sort of outpatient services to have you be seen probably on a weekly basis for awhile to help ensure you stay off the meds. (Best to have insurance to use this- so if you don't, you might have to call around).
Support groups, like Narcotics Anonymous, might also be helpful for you. Perhaps look up some local meetings, go to one and see if they can offer some words of advice and support to help point you in the right direction for a detox facility or something else to help you go through the withdrawal.
http://www.na.org/ Narcotics Anonymous
If your husband has a similar addiction this will make it very difficult for you to stay clean. In this case, it would be best if you could convince him to do this with you. Obviously there are huge implications if this were ever discovered at work or elsewhere since you could face legal trouble. So perhaps try to find what part of his life it will speak to him the most and approach from that angle.
Sometimes it takes walking away before the person realizes they have a problem. Are you ready to do that? It's most important to take care of yourself first, and him a close second (assuming no kids are in the house...). So if he refuses to do anything, that's a detriment to you and I would suggest acting accordingly. Maybe then he'll get the picture.
Quitting takes a degree of committment and the ability to persevere even when you're miserable- so I commend you for wanting to take that step. You've taken the biggest one so far- realizing there's a problem and deciding it needs to stop. The rest will hopefully follow close behind- though it won't be easy it will be worth it.
Best wishes to you and your husband. I hope you will both overcome soon!